Non-vibrational dental tool



Aug. 27, 1963 F. H. FODOR NoN-VIBRATIONAL DENTAL TOOL Filed NOV. '7. 196

IN V EN TOR. E FOOR [REA/Z rroe/v ys.

United States Patent O 3,101,542 NN-VlERATiUNAL DENTAL TQL Ferenz H. hedor, 7463 Melrose Ave., Los Angeles 46, Calif.

Filed Nov. 7, 1960, Ser. No. 67,811, 14 Claims. (Cl. 32-Z7) This invention relates to a dental tool and more particularly, to a very smooth running, high-speed drilling tool having exceptionally low vibration characteristics, whereby the tool is particularly adapted for dental and surgical use.

With the advent of the use of high-speed drilling tools in the dentistry profession, ythe proiiciency with which a vdentist may drill cavities in teeth has been greatly increased and the pain normally encountered by a patient during such drilling operations has been considerably reduced. Such reduction in pain encountered by the patient is generally -due to the higher cutting speeds now ernployed which allow the completion of a drilling operation before the temperatures of the tooth and cutting tool become high enough to disturb the adjacent nerve endings.

The reduction in cutting temperature by increased cutting speed, however, has been accompanied by an increase in vibration of the cutting tool due to the higher r.p.m. of the rotating parts employed. It has been found that vibration is a major cause of pain experienced by the patient during a drilling operation due to aggravation of the nerve endings near the drilling area. In addition, when very high drilling speeds are used, there is a tendency for the drill to continue turning after the driving mechanism-is de-energized due to the large inertia forces built up at such high speeds. A deeper cavity than desired is frequently, though inadvertently, thereby drilled. The difference between a very uncomfortable toothache and a successful drilling operation may depend on whether the drill stops turning in rapid response to the twill of .the operator. Furthermore, after drill penetration of the tooth enamel, slower drilling speeds are preferable due to the softer inner tooth mate-rial, dentin and pulp, and due to the proximity of the drilling tool with the nerve center of the tooth.

lt is, therefore, a primary object of this invention to disclose and provide a high-speed dental drilling tool which is very smooth running, and substantially free of nerve aggravating vibration.

It is another object of this invention to disclose and provide an adjustable-speed dental drilling tool which may be rapidly started and stopped at the will of the operator.

A further object of the invention is to disclose and provide a substantially gearless driving mechanism employing permanent magnet couplings and friction drive connections to obtain smooth non-vibrational operation of a drilling tool. f

A still further object of this invention is to disclose and provide an easily manipulated, self-contained, nonvibrational drilling tool easily manipulated while drilling teeth in a patients mouth, which is economical to manufacture, portable to be easily carried and sterilized, and possesses a long useful life.

Generally stated, the invention comprises a hollow separable body portion, preferably composed of three housings or shell members; an elongated power drive shell, a central handpiece shell and a headpiece shell. The elongated power drive shell is provided with motor drive means preferably in the form of an electric motor of the adjustable speed type positioned in the rearward portion of the power drive shell. The motor shaft extends forwardly within the power drive shell. A speed reducing drive assembly may be optionally provided immediately forward of the motor as part of the motor drive means 3, E E Patented Aug. 27, l 963 "ice and is engaged by a forward portion of the motor shaft. Such an assembly may be provided to improve motor torque of the commonly used small high speed electrical motors. This speed reducing drive assembly may be omitted when a suitably high speed, high constant torque motor of small size is employed. Immediately forward of the motor drive means there is provided a selectively operable magnetic clutch means which is associated with the motor drive means and when operated, engages a clutch shaft connecting it to the motor drive means. A magnetic brake assembly is also provided in association with the clutch shaft to effect a rapid stopping of the drill when operating even at very high speeds.

ri'he centrally located handpiece shaft is of virtually cylindrical dimensions to be easily manipulated and contains a handpiece shaft which is driven by the clutch shaft by Way of a positive mechanical connection between the two.

A magnetic coupling comprised of two permanent magnet members, preferably made of ceramic permanent magnet material, is provided in the forward portion of the handpiece shell coupling the handpiece shaft to a coupling shaft in the headpiece shell. Such connection tends to eliminate any jerky, sporadic movements or vibrations caused by the motor drive means.

The aforementioned coupling shaft, provided in the headpiece shell, transmits the driving power of the motor means from the magnetic coupling to a drilling tool through a driving connection between the two. In addition, a magnetic chuck may be provided in association with the driving connection to magnetically hold and position a drilling tool relative to the headpiece in operable position.

A more detailed description of exemplary embodiments of the non-vibrational dental tool according to the invention will be hereafter presented with references made to the appended sheet of drawings in which:

FIG. l is a side elevation of the exterior of a non-- vibrational dental tool according to the invention;

FIGS. 2 and 2a -are a side sectional view of the dental tool of FIG. l sectioned longitudinally along a vertical plane passing generally through the central `axis of the tool;

FlG. 3 is a cross sectional view of the dental tool of FIG. 2` along the plane IIL-III;

FIG. 4 is an alternative embodiment of a portion of the dental tool of FIG, 2a;

FIG. 5 is another alternative embodiment of a portion of the dental tool of FIG. 2a; and

FIG. 6 is ia detail view of a portion of the alternative embodiment of FIG. 5 along the plane VV.

Referring first to FIG. l, the non-vibrational dental tool, according to the invention, comprises a hollow separable body portion preferably constructed of three shell or housing members which enclose the driving mechanism of the tool. The central housing member, as shown in FIGS. l, Z and 2a, is a straight hand piece shell Iconsisting of va virtually cylindrical hollow handpiece adapted to be easily grasped and manipulated.' The rear end of the handpiece shell l, as seen in FIG. 2, lis provided with an internal taper to receive the interconnecting holding member 2. Holding member 2 is of a generally frustroconic external configuration having a ilange area 3 at the larger rearwardly facing end and has a bore 4 axially aligned therethrough. The internal taper of the rear end of the handpiece shell 1 mates with the external taper of the interconnecting hold-ing member Z to effect a tight or press t maintaining the )two par-ts in an interconnected assembled relationship.

A handpiece shaft 5 is axially journalled within the handpiece shell l by means of fthe ball bearings 6 and 7,

as shown in FIGS. 2 and 2u. The forward end of the handpiece shaft 5 is adapted to receive a magnetic coupling member 8, which is preferably of two diameter cylindrical construction having a generally T shaped cross section and presents a forwardly facing, generally circular surface, or face. The rearward end of the handpiece shaft 5 is tapered toward that end to be readily inserted and received within the bore of a clutch shaft 9. Handpiece shaft 5 and clutch shaft 9 may be made in one piece but the embodiment here shown is preferable to allow ease of assembly and disassembly of the tool. The forward bearing 7 abuts against the magnetic coupling member 8 and the rearward bearing 6 abuts. against the interconnecting hold-ing member 2. A tubular separator 10 is provided to separate and position the bearings 6 and 7 relative to the handpiece shaft 5 positioning the non-rotating outer race portion o-f the bea-ring 6 in abutting engagement with the member 2 and the rotating 4inner race of bearing 7 kagainst the rotatable coupling 8. A sleeve 10" may also be employed to hold and position the outer races of ball bearings 6 and 7 within the handpiece shell 1 by a frictional fit between the sleeve 10 and shell 1, and between sleeve 10 and ball bearings 6 and 7.

The rear housing is an elongated power drive shell 11 which may be removably mounted upon the' rearward end of the handpiece shell 1, in axial alignment therewith, by means of the interconnecting holding member 2. Power drive shell 11 is preferably a virtually cylindrical shell closed at its rear end except for an oil hole 12 and open at its forward end. The forward end of shell 11 is taped to provide `an internal thread to allow the shell 11 to be removably screwed onto external threads on the ange 3 of the interconnecting member 2, effecting the connection indicated generally `at 13 in FIG. 2.

High-speed electrical motor drive means are provided adjacent therearward end of the separable 'body' of the tool, as shown in FIG. 2, wherein Ia motor 14 is positioned within :the power drive shell 11 toward the rearward end Yof shell 11. Since the dental .tool is most effective when operated a-t high speeds `and it is also desirable to be able to adjust the speed of the motor, a suitable: adjustable speed, normally polyphase, A.C. motor should be emplo-yed. I have found that a -two phase, 4 pole, 400 cycle, 26 volt, A.C. motor is particularly suitable for use in my Non-,Vibrational Dental Tool. A motor shaft 15 is journalled on ball bearing 16 at the rear wa'll of the power drive shell 11 'and on ball bearing 17 at a ported divider wall 18. Ported divider wall 18 may be positioned within shell 11 by providing raised beads 18 on the inner surface of the power drive shell 11 and is ported to allow the motor shaft 15 to pass therethrough.

A speed reducing drive assembly, indicatedgenerally 'at 20 in FIG. 2., may a-lso be optionally provided within the power drive shell 11, Iforward of the motor 11 and separated therefrom by the divider Wall 18, to Iact as part of the motor driving means when greater motor torque is required than the particular motor employed will provide without reduction gearing. Motor shaft 15 extends forwardly through the divider wall 18` where a forward portion 15 cooperates with and drives the optional speed reducing drive assembly. As shown in the embodiment 'of FIG. 2, 4the `assembly consists of a cylindrical cup-like housing member 21, having a cover plate `22; an internal gear 23; and a pinion 24. The cup-like housing member 21 is provided with a rearwardly directed open end to receive the vplate 22 `and a `forwardly directed ported end to receive the drive shaft 27. Cover plate 22 is adapted to close the rearwardly directed open end of the cupelike housing member 21 and is ported to receive .therethrough the forwardly extending motorshaft 15. Pinion 24 is rotatably journalled upon the cover plate 22 in the upper v half of the housing member 21 4by means of the shaft 25. Shaft 2S is fixed within Ythe bore of the pinion 2t and journalled within a ball bearing 26, which in turn is xedly mounted within the cover plate 22. Pinion 24 is thereby positioned within the cup housing member 21 of the speed reducing drive `assembly to be engaged and driven by the forward gear portion 15 of the motor shaft 15. The pinion 24, in turn, drives the internal gear 23, effecting a reduction of the motor speed 'and an increase in torque, promoting smooth running characteristics of the tool. Internal -gear 2,3y is mounted on the drive shaft 27, which is journalled in the forward wall of the planetary drive housing 2-1 by means of the ball bearing 28, and is thereby adapted to cooperate with the selectively operable magnetic means indicated generally at '30. When a constant torque high speed electric motor having superior -torque producing characteristics -is employed, the motor shaft 15 and drive shaft 27 may be provided as one integr-al shaft. Such embodiment is preferred.

Selectively operable magnetic means are provided to selectively drive and stop the drilling tool. Such means are comprised of selectively energized magnetic clutch means and non-rotating magnetic brake means.

The magnetic clutch means, also contained within the power drive shell 11, is comprised of an electromagnet 31 and la spring finger assembly 32. The magnetic clutch is a form of friction 'clutch in which the friction surfaces are brought into contact byy electro-magnet 31 instead of by some mechanical means. An advantage of this clutch is .that it may be operated at higher rotative speeds than mechanical clutches and stands up well under heavy duty high speed driving. Electro-magnet 31 is preferably of generally ring construction ladapted to present a forwardly facing generally flat annular surface and is rotatably mounted upon the magnetic drive shaft 27. Electromagnet 31, therefore rotates along with the drive shaft 27 as the latter is impelled by the motor driving means. Spring finger assembly 32 is positioned in register with the forwardly facing annular surface of the electromagnet 31 by being iixedly mounted on the clutch shaft 9, which is in substantial axial alignment with the drive shaft 2.7 and motor shaft 15. The assembly 32 is comprised of individual spring fingers il?)l 'and a ring 34 about the periphery, as shown in FIG. 3.

Upon energization of the electromagnet 31, the ring 34 and spring fingers 33` of the assembly 32, being preferably made of a ferrous material, are attracted to and are magneticall-y bound to the electromagnet 31, effecting a connection between the drive shaft 27 `and the clutch shaft 9. The rotation of the handpiece shaft 5 may, therefore, be rapidly started, the motor 14 being already in operation,

by merely completing a circuit to lthe electromagnet 31 Y and thereby causing the clutch means to be rapidly engaged.

A magnetic brake assembly is. also provided within the power drive shell 11 just yforward of the magnetic clutch means. A brake spring linger -assembly 36, having spring fingers bounded by a ring member `similar to assembly 32, is mounted on the clutch shaft 9 forward of the spring nger assembly 32 and presents a forwardly facing surfacel to Icontact an electrom-agnet 37. Electromagnet 37 is preferably of generally ring c-onstruction, presenting a rearwardly facing ygenerally flat annular surface, and is xedly, non-rotatably mounted on the rear wall of the interconnecting holding member 2. The ring member and Aspring fingers of brake spring linger assembly 36 are positioned in register with such rearwardly facing surface o-f electromagnet 37. The energizing of the electromagnet 37 by mean-s of a suitable electric circuit causes the brake spring fingers and ring member of assembly 36, being preferably made of a ferrous material, to be attracted to and bound against the rearwardly facing annular surface of the electromagnet 36. To stop the hand-piece shaft 5, the magnetic clutch means, indicated generally at Sil, is deenergized and the magnetic brake assembly is simultaneously activated. Such operation stops the shaft rotation Very rapidly by the braking action of the brake spring linger assembly 36 binding against the brake electromagnet 37.

The clutch elements, clutch spring finger assembly 32 and the brake spring finger assembly 36, may be provided as a single element which would Ialternately engage the electromagnets 31 and 37. However, the embodiment shown in PIG. 2 is preferable since the air gap between yassembly 32 and electromagnet Sill and between assembly 36 and electromagnet 37 may be readily adjusted by providing adjustable spring means extending between the fingers of 'assembly 32 and -assembly 33'. By varying the tension in such spring means, the air gaps may be equally enlarged or narrowed as desired by pulling the finers of the two assemblies nearer together or allowing them to relax to a normal position in which the ring memt ers of the assemblies are in close proximity to the electromagnets. Such spring means may be provided by attaching tension springs between various aligned fingers of the two assemblies, which, as shown in FIG. 2, have a common hub 35 mounted on the clutch shaft 9. The tension spring ends may be attached to the spring fingers by screws or bolts which may be screwed in =or out of the fingers to vary the tension in the springs.

lt may be seen, therefore, that by the use of such magnetic clutch means and a magnetic brake means, together with a suitable power source, wiring and switches of conventional types, the handpiece shaft 5 is adapted to be very rapidly vaccelerated to the rpm. of the drive shaft 2.7, the motor driving means being. already in operation turning the drive shaft Z7 at a high r.p.m., and may also be very rapidly decelerated to a stopped position, at the will of the operator. The forces created in such rapid .starting and stopping yof the shaft 5 are distributed over the circular faces of the electromagnets 31 and 37 such that an even distribution of load is provided. Such distribution of the starting and stopping torque loads restrains vibrations and jerking motions to a minimum.

The forward `housing member, as shown in FIG. 2a, is an angle headpiece shell `iti which is removably mounted on the forward end of the handpiece shell 1. As seen in FIG. 2a, the headpiece shell 4b isvpreferably of a right angle generally :cylindrical construction with a coupling shaft `4l journalled therein in substantial axial alignment with the handpiece shaft S. A drill i2 is axially journalled therein at generally right angles to the axis of the coupling shaft 4d and the handpiece shaft S. I-leadpiece shell id is preferably removably attached to a cylindrical coupling shell 43% by means of a threaded, screw type Iconnection at 44. The coupling shell 43 is, in turn, removably connected to the forward end ofthe handpiece shell 1 by the threaded connection at 45.

Coupling shaft di is journalled on the ball bearings 46 and 47 and is provided with a magnetic coupling member Z13 on -its rearward end. Coupling member i8 is preferably yof .two diameter cylindrical construction, having a lgenerallyvT shaped cross -section and presents a rearwardly facing circular surface or face adapted to contact the forwardly facing magneticcoupling member 8 on the forward end of :the handpiece shaft 5.

rihe coupling members 8 and i3 are permanent magnets which adhere to each other to effect a magnetic coupling. Such permanent magnets may be made of Alnico or of ceramic permanent magnet material. I have found that ceramic permanent magnets, pressed and formed from ceramic material, are preferable since they provid-e very good, workable magnets that are less expensive than corresponding metal magnets. The magnetic coupling formed by the coupling members 8 `and 48 provides a very a smooth running coupling which transmits the driving power of the handpiece shaft 5 to the coupling shaft dll. The forward end of the lcoupling shaft 4l is provided with a permanent magnet 49 made of Alnico or, preferably, a ceramic permanent magnetic material. The inner rotating races yof the bearings de and 47 abut against the permanent magnets 48 and 49, respectively, and are separated and positioned by a tubular separator 5d.

Headpiece shell 40 is also provided with a -driving connection between the coupling shaft fil, and, therefore, handpiece shaft 5, and the drill 42. Such connection as shown in FIG. 2n is comprised of the permanent magnet 49, acting as a burr :drive member, axially mounted on the forwarded end of the coupling shaft il and -a friction disk Si. The burr 49 is a generally round, trod-like member with an enlarged head portion at the forward end.

`Friction disk 5l is preferably made of a ferrous material, responsive to the magnetic attraction exer-ted thereon by the permanent magnet burr 49, and is provided with a rectangular bore to receive a portion 'of the drill 42. Friction disk 51 is axially journalled within the headpiece .shell d@ with its axis at a generally right angle to that of the burr 49 by means of the ball bearings 52 and 53 so that it is positioned to be rotated by the burr 49. The surface 54 of the burr i9 and the surface '55 of the disk 511 are adapted to mate with each other in a magnetic friction drive connection, the disk 5l being positioned below the burr i9 in the lower portion of the headpiece shell with A permanent magnet chuck 56 made of Alnico` or, preferably, of ceramic permanent magnet material, may also be provided within the headpiece shell ed' in association with the friction disk Sill. The magnetic chuck 56; is preferably of a `generally disk-'like configuration suitable to be magnetically attracted to and thereby engage the underside of the friction disk 5l effecting a magnetic coupling.

Chuck 56, being a permanent magnet, is adapted to magnetically hold the drill 42, preferably made of a ferrous material, with sufficient force to maintain it in position during la Vdrilling operation yet allow relatively easy disengagement of the drill 42 manually. Drill 42 may be provided with a circular plate or disk-like portion 58 to provide surface area to effect suchmagnetic engagement of the drill d2 to the underside of the chuck 56. A ring holder 57 may be also employed to provide a guide member to guide and laterally restrain the rotating disklike portion -SEB of drill 4t2.

The shaft of drill 4t2 is preferably provided with arectangular cross section such that when positioned w1th1n the rectangular bore 'of friction disk 5l, a mechanical connection is obtained between the drill #i2 and disk 5l. The magnetic chuck 56 is also provided with a bore of sufficient diameter to allow the shaft` of drill 42 to pass up into the cylindrical pillar portion of the disk member 5l which is journalled on the ball bearing 52. The drill 4.2 is rotated along with the chuck 56 by the disk 51 as the burr drive member 49 drives the disk 5l.

The provision of this magnetic driving connection and the use of magnetic couplings, according to the lnventron, produce a very smooth running vibration free dental tool which is particularly adapted for use at very high rotation speeds. Furthermore, the positioning of the optional planetary drive assembly with the pinion 24 in the upper portion of the housing 21 and the driving contact area between the burr 49 and disk member 51 in the lower portion of the headpiece shell di) causes. the torque producing loads in the two areas to be out of phase and thereby offsetting of each other. A smoothconstant drive is thereby promoted avoiding sporadic movements on starting Xand stopping of the tool as well as undue vibrations or erratic motion of the tool ldue to its high speeds of rotation when employed in high speed drilling operations.

An alternative construction of the invention is shown in FIG. 4. ln this alternative embodiment, the headpiece shell 6b is straight and of generally cylindrical construction having a coupling shaft 61 rotatably journalled therein on the ball bearings 62 and 63, which are separated by a tubular separator 66. A permanent magnet coupling member 64- is provided on the rearward end of the shaft 6l to couple with the coupling member 8 of the dental tool of FIG. 2a. A permanent magnet chuck 65 may be provided on the forward end of the shaft 6l to hold and position the drill 42. The rectangular shaft of 'i drill 42 may be inserted into the bore of shaft 6l. which is of suitable rectangular congunation to effect a driving connection therebetween.

IThe drill 42 is, therefore, rotated by the shaft 61 in response t'o the operation of the dental tool by the operator through the magnetic coupling effected by coupling members 8 and 64.

Another alternative embodiment of a dental tool according to the invention, is shown in FlG. 5. Here the coupling shell '70' is `provided with a bend at its rearward end to provide an angled relationship between the headpiece shell Si) :and the handpiece shell 1. The coupling shaft is provided in two parts, forward shaft 7l journalled on the ball bearing 72 and a rear shaft 73 journalled on the ball bearing 74, thev two shafts being axially aligned with each other but describing an obtuse angle therebetween. An angled magnetic drive is provided between the shaft 7l and the shaft 73 in the form of a permanent magnet drive member 75, provided on the forward end of rear shaft 73 and presenting a forwardly facing generally convex surface, and a 'permanent magnet driven member 76 provided on the rearward end of forward shaft 7l and having .a rearwardly facing, generally concave surface, the convex and concave surfaces of the respective magnets meeting in an angled magnetic friction drive connection.

`The headpiece shell 80 may also alternatively be provided with an adjustable swinging head of a generally ball and socket type. As shown in FIG. 5, the headpiece shell Sil may be provided with a socket mem-ber 8l, shown therein in cross section. An inner 4ball `head member 82 is positioned therein and is held into the socket 8l and restrained into arcuate rotation in one plane only by Va dovetail or gib 83 which slides within a way or spline 84 in the socket lSil. A slot 85 is provided within the inner ball head member 82, the gib S3 terminating at said slot, to allow the inner head member 82 to swing within the socket 81 without binding upon the shaft 7l.

The driving connection between Ithe coupling shaft 7l and the drill 42 in the embodiment of FIG. 5 comprises the permanent magnet 86, having la forward ball head acting as a burr drive member. Friction disk 87 is mounted in the -radial bearing 53 and is provided with a convex surfaced portion 38 which is engaged and frictionally driven by the permanent magnet 86. The frictional drive between disk 87 and burr 86 is enhanced b-y the magnetic attraction exerted by permanent magnet burr 86 upon the preferably metallic disk 87. The magnetic chuck 56 holds drill 42 in place against disk 87, the drill 42 being guided by the ring holder 57. A mechanical drive connection may be effected between drill 42 yand disk 87 by providing a rectangular bore within disk 87 into which la rectangular portion of the shaft or shank of drill 42 may engagingly protrude.

The exemplary embodiments of the non-vibrational dental tool described herein in detail are not intended to be exhaustive of all possible embodiments of the invention and it -should be understood that other modifications, alterations and embodiments may be made within Ithe scope of myinvention as defined by the following claims:

I claim:

l. A hand-held, smooth running, easily manipulated, non-vibrational dental tool comprising: a virtually cylindrical hollow bandpiece shell having a handpiece shaft axially journalled therein, saidr handpiece shaft .having a forwardly facing permanent magnet coupling member carriedon a forward end of said handpiece shaft; an

elongated power-drive shell removably connected to a rear end `of said handpiece shell and in axial alignment therewith, said power-drive shell containing ran electric motor, a speed reducing drive operably connected thereto and a clutch shaft in axial alignment therewith; magnetic clutch means adapted to selectively connect the speed reducing drive to the clutch shaft; a magnetic brake assembly associated with said clutch shaft, said clutch shaft being lin axial alignment with and being adapted to driv- S ingly engage the handpiece shaft in all positions of the magnetic clutch and brake assembly; a headpiece shell removably attached to the lforward end of said handpiece shell, said headpiece shell including a coupling shaft journalled therein, said coupling shaft carrying a permanent magnet coupling member having a rearwardly ,directed face adapted to contact the forwardly facing permanent magnetic coupling member of said handpiece shaft; and 4a driving connection between said coupling shaft and a drilling tool mounted within said headpiece shell.

2. A handheld, smooth running, easilymanipulated, non-viltnra'tional dental tool comprising: a virtually cylindrical hollow handpiece shell Vhaving a handpieoe shaft Iax-ially journalled therein, said handpiece shaft having a forwardly facing permanent magnet coupling member carried on a forward end of said handpiece shaft; an elongated poweredrive shell removably connected to a rear end of said handpiece shell and in axial alignment therewith, said power-drive shell containing an electric llike housing axially aligned |within the power drive shell having a rearwardly directed open end and a forwardly directed ported end; a drive shaft extending into said cup-like housing through said forwardly directed ported end; an internal tooth gear rotatably mounted within said cup-like housing in axial alignment therein and mounted upon said clutch shaft, a cover plate adapted to close said rearwardly directed open end of said cup-like housing, said plate being ported to `receive therethrough said forwardly extending motor shaft; and a pinion rotatably mounted on said cover plate within said cup-like housing and adapted to interengage said motor shaftand said internal tooth gear.

3. A non-vibrational ydental Itool as in claim 2 wherein said driving connection in sai-d headpiece shell comprises:

a permanent magnet burr drive member axially mounted on a forward end of said coupling shaftin axial alignment therewith, said burrv having an enlarged forward head portion; and a friction disk member axially `journalled within said headpiece shell with its axis at a Igenerally right angle to that of said drive member, the disk being adapted v to be rotated about its axis by the rotation of said burr about its own 1axis by said head portion of said burr contacting said disk in a magnetic friction drive; and wherein said pinion is positioned within said cup-like housing in an upper portion of said housing and power drive shell, and said friction disk member is located within said headpiece shell in a lower portion of said shell beneath said vburr driver.

4. A hand-held, smooth running, easily manipulated,

y non-vibrational dental tool comprising: a virtually cylindrical hollow handpiece shell having la handpiece shaft axially journalled therein, said handpiece shaft having a forwardly facing permanent magnet coupling member carried on la forward end of said handpiece shaft; an elongated power-drive shell removably connected to a rear end of said handpiece shell and in axial alignment therewith, said power-drive shell containing an electric motor, a speed reducing -drive operably connected thereto land a clutch shaft in axial alignment therewith, magnetic clutch meansV adapted to selectively connectthe speed reducing drive to the clutch shaft; a magnetic brake assembly associated with said clutch shaft, said magnetic brake assembly including a non-rotating eleetromagnet xedly mounted within said power-drive shell presenting a generally flat, reanwardly facing, angular face, anda brake spring finger assembly iixedly mounted on said nular surface in substantial register with said rearwardly `a headpiece shell removably attached to the forward end of said handpiece shell, said headpiece shell including a coupling shaft journalled therein, said coupling shaft carrying a permanent magnet coupling member having a rearwardly directed `.face adapted to contact the forwardly facing permanent magneticcoupling member of said handpiece shaft; yand a` driving connection between said coupling shaft and a drilling tool mounted within said headpiece shell.

5. A hand-held, smooth running, easily manipulated, non-vibrational dental tool comprising: a virtually cylindrical hollow handpiece shell having a handpiece shaft axially journalled therein, said handpiece shaft having `a forwardly facing permanent magnet coupling member carri-ed on a forward yend ofsaid handpiece shaft; an elongated power-drive shell removably connected to a rear end of said handpiece shell and in axial alignment therewith, said power-drive shell containing an electric motor, a speed reducing drive operably connected thereto and a clutch shaft in yaxial alignment therewith; magnetic clutch means adapted to selectively connect the speed reducing drive to the clutch shaft; a magnetic brake assembly associated with said clutch shaft, said clutch shaft being in axial alignment with and being adapted todrivingly engage the handpiece shaft in all positionsy of the magnetic clutch and brake assembly; a headpiece shell removably attached to the forward end of said handpiece shell, said headpiece shell including a coupling shaft journalled therein, said coupling shaft carrying a permanent magnet coupling member having a rearwardly directed face adapted toy contact the forwardly facing permanent magnetic coupling member of said handpiece shaft; and a driving connection between said coupling shaft and a drilling tool mounted within said headpiece f shell, said driving connection including a permanent magtnet driving memlber provided on a forward end of said coupling shaft anda friction disk axially disaligned with said coupling shaft and associated with said drilling tool to provide common rotation of said disk and said drilling tool, said disk being adapted to be rotatably driven by said permanent magnet driving member.

6. A hand-held, smooth running, easily manipulated, non-vibrational dental tool comprising: a virtually cylindrical hollow handpiece shell having a handpiece shaft axially journalled therein, said handpiece shaft having a forwardly facing permanent magnet coupling member carried von a forward end of said handpiece sha-ft; an elongated power-drive shell removably connected to a rear end of said handpiece shell and in axial alignment therewith, said power-drive shell containing an electric motor,

la drive shaft associated 'with said motor, and a clutch shaft in axial alignment therewith; magnetic clutch means adapted to selectively connect the motor associated drive shaft with said clutch shaft; a magnetic brake assembly associated with said clutch shaft; said clutch shaft being in axial alignment with and being adapted to drivingly engage the handpiece shaft in all positions of the magnetic clutch and brake asembly; a headpiece shell removably attached to a forward end of said handpiece shell, said headpiece shell including a coupling shaft journalled therein, said coupling shaft carrying a permanent magnet coupling member having a rearwardly directed Iface adapted to contact the forwardly facing permanent magnet coupling Amemberof said handpiece shaft; and a driving connection between said coupling shaft and a drilling tool mounted within said headpiece shell, said driving connection including a permanent magnet driving lmember provided on a forward end of said coupling shaft and a `friction disk axially disaligned with said Icoupling shaft and associated with said drilling tool to provide common rotation of said disk and said drilling tool, said disk being adapted to be rotatably `driven by said permanent magnet driving member.

7. A non-vibrational dental tool as in claim 6l wherein said headpiece shell is provided withv a magnetic chuck associated with said disk member to magnetically hold and position said drilling tool relative to said headpiece shell, said magnetic chuck being a disk-like permanent magnet positioned against the underside of said friction disk.

8. A hand-held, smooth running, easily manipulated, non-vibrational dental tool comprising: a virtually cylindrical hollow handpiece shell having a handpiece shaft axially journalled therein, said handpiece shaft having a forwardly facing permanent magnet coupling member carried on Ia forward end of said handpiece shaft; an elongated power-drive shell removably connected to a rear end of said handpiece shell andrin axial alignment therewith, said power-drive shell containing an electric motor, a speed reducing drive operably connected thereto and a clutch shaft in axial alignment therewith; a magnetic clutch means adapted to selectively connectthe speed reducing drive to the clutch shaft; a magnetic brake assembly associated withsaid clutch shaft, said clutch shaft being in axial alignment with and 1being adapted to drivingly engage the handpiece shaft in all positions of the magnetic clutch and brake assembly; 4a headpiece shell removably attached to the forward end of said handpiece shell, said 'headpiece shell including a coupling shaft journalled therein, said coupling shaft carrying a permanent magnet coupling member having a rearwardly directed face adapted to contact the forwardly' facing permanent magnetic coupling member of said handpiece shaft; a driving connection between said coupling shaft and a drilling tool mounted within said headpiece shell, said driving connection including a permanent magnet driving member provided on la forward end of said coupling shaft and a friction disk axially disaligned with said coupling shaft and associated with said drilling tool to provide common rotation of said disk and said drilling tool, said disk being adapted to be rotatably driven by said permanent magnet driving member; and a magnetic chuck provided within said headpiece shell and associated with said driving connection to magnetically hold and position said driil within said headpiece shell, said magnetic chuck being a disk-like permanent magnet.

9. A hand-held, smooth running, easily manipulated, non-vibrational dental tool comprising: a virtually cylindrical hollow handpiece shell having a handpiece shaft axially journalled therein, said handpiece shaft having a forwardly facing permanent magnet coupling member carried on a forward end of said handpiece shaft; an elongated power-driven shell removably connected to a rear end of said handpiece shell and in axial :alignment therewith, said power-drive shell containing an electric motor, a drive shaft associated with said motor, and a clutch shaft in Iaxial alignment therewith; magnetic clutch means adapted to selectively connect the motor associated drive shaft wtih said clutch shaft; a magnetic brake assembly associated with `said clutch shaft; said clutch shaft being in axial alignment with and being adapted to drivingly engage the handpiece shaft in allpositions of the rnagnetic clutch and brake assembly; a headpiece shell removably attaohed to a forward end of said handpiece shell, said headpiece shell including a coupling shaft journalled therein, ysaid coupling shaft carrying a per-manent magnet coupling member having a rearwardly directed face adaptv ed to contact the forwardly facing permanent magnet couon'a forward end of said rear shaft and presenting a forwardly facing, generally convex surface and a permanent magnet `driven member provided on a rearward end of said forward shaft having a rearwardly facing, generally concave surface, said convex and said concave surfaces of said permanent magnets meeting in an angled magnetic friction drive connection.

10. A non-vibrational, virtually gearless drilling tool comprising: a hollow, separable body portion provided with ay high speed electrical motor drive means contained adjacent one end of such body portion; a magnetic chuck carried by the other end of said body portion, said other `end of said body portion extending at an angle to the remainder of the body portion; a shaft journalled 4between `said chuck and motor means, said shaft including two sections thereof with axes at an angle to each other; and permanent magnet |coupling members carried by said shaft sections forming 1a driving connection therebetween, said coupling members including opposed permanent magnets engaging each other in a magnetic friction drive connection wherein one permanent magnet is provided with a generally convex contact surface and the other of vSaid f magnets lis provided with a generally concave contact surface. k f

l1. In 1a non-vibrational, virtually gearless drilling tool having a body portion provided with a high speed elec trical motor drive means contained adjacent one end of 'said body portion, a drilling tool chuck carried by the other end of said Ibody portion; la shaft journalled in said body portion and extending between said chuck and motor means; and selectively `operable clutch means for engaging 'and disengaging said motor means with said shaft, the

provision of: a permanent magnet driving member on a forward end o-f said shaft and a friction disk axially disaligned with said shaft and associated with said drilling tool chuck to provide common rotation 'of said disk and chuck, said disk being adapted to be rotatably driven by said permanent magnet driving member.

12. In a non-vibrational dental tool having a hollow, separable body portion provided with a high speed electrical motor drive means `contained adjacent one end of such body portion; a drilling tool carried by the other end of said body portion, a shaft journialled within said body Vportion and between said drilling tool and motor means;

and selectively operable clutch'means for engaging and disengaging said motor means and said shaft, the provision of: a permanent magnet driving member on a forward end of said shaft, a friction disk axial-ly disalgned with said 'coupling shaft adapted to be rotatably driven by said permanent magnet driving member, and la magnetic chuck associated with' said `disk member and body portion to 'magnetically hold and position a drilling tool relative t( said body portion, said Y magnetic chuck being a disk like penmanent magnet positioned against an underside o1 said friction disk to provide corn-mon rotation of said disk,

v magnetic chuck and drilling tool.

13. A hand-held, smooth running, easily manipulated, non-vibrational dental tool comprising: a virtually cylin- `drical hollow handpiece shell having a handpiece shaft axially journalled therein, said handpiece shaft having a forwardly facing permanent magnet coupling member carried on a forward end of said handpiece shaft; an

- l2. yelongated power-drive shell removably connected to a rear end of said `h-andpiece shell `and in axial alignment therewith, fsaid power-drive shell containing anelectric motor, a drive shaft :associated with said motor, and a clutch shaft in axial alignment therewith; magnetic clutch means adapted to selectively connect the motor associated drive shaft with said clutch shaft; a magnetic b'nake assembly associated with said clutch shaft;`said clutch shaft being in axial alignment with and being adapted to driv- :in'gly engage the handpiece shaft in all positions of the magnetic clutch and brake assembly; a' headpiece shell rei movably attached to -al forward end of said `handpiece shell,

said headpiece shell including a coupling shaft j'ournalled therein, said coupling shaft carrying a permanent magnet coupling member having a rearwardly directed face lectively operable magnetic means for disconnecting said motor means yfrom said shaft and ypositively stopping rotation of said shaft, said selectively operable magnetic `means including: a tir-st electromagnet rotatable by said motor means and having a generally flat, forwardly flacing annular surface; a non-rotatable second electromagnet Xedly mounted within said body portion spaced from .said first electromagnet rand having a generally flat rearwardly facing annular surface; and two spaced spring finger assemblies fixedly mounted on said shaftga first spring linger assembly of said 4assemblies having a rear- `-wardly facing annular surface in substantial register with said forwardly facing annular sunface of 'said first electrornagnet and Ibeing adapted to be ymagnetically attracted to said first electnomagnet upon its energization to effect a magnetic friction engagement between said shaft and said motor means, a sond spring `linger assembly lof vsaid assemblies having a forwardly facing annular sur- Iface in vsubstantial register with said 'rearwardly facing annular surface of said non-rotating second-electromagnet i ,and being adapted to be magnetically attracted to said second electnomagnet upon its energization to effect a braking `action on said shaft.

References Cited in the le of this patent UNITED STATES PATENTS 903,222 McMahon Nov; 10, 1908 1,201,362 Shelton 'Oct. 17, 1916.1 1,379,880 Seaborn May 31, 1921-V 1,476,976 Ivory Dec. 11, 1923' 2,010,421 Terry Aug. 6, 1935 2,560,868 Hubert .Iu1y 17, 1951 2,876,878 Sinclair et al. Mar. 10, 1959 2,966,977 Johnson Jan. 3, 1961 2,990,616 Balamuth et `al July 4, 1961 

11. IN A NON-VIBRATIONAL, VIRTUALLY GEARLESS DRILLING TOOL HAVING A BODY PORTION PROVIDED WITH A HIGH SPEED ELECTRICAL MOTOR DRIVE MEANS CONTAINED ADJACENT ONE END OF SAID BODY PORTION, A DRILLING TOOL CHUCK CARRIED BY THE OTHER END OF SAID BODY PORTION; A SHAFT JOURNALLED IN SAID BODY PORTION AND EXTENDING BETWEEN SAID CHUCK AND MOTOR MEANS; AND SELECTICELY OPERABLE CLUTCH MEANS FOR ENGAGING AND DISENGAGING SAID MOTOR MEANS WITH SAID SHAFT, THE PROVISION OF: A PERMANENT MAGNET DRIVING MEMBER ON A FORWARD END OF SAID SHAFT AND A FRICTION DISK AXIALLY DISALIGNED WITH SAID SHAFT AND ASSOCIATED WITH SAID DRILLING TOOL CHUCK TO PROVIDED COMMON ROTATION OF SAID DISK AND CHUCK, SAID DISK BEING ADAPTED TO BE ROTATABLY DRIVEN BY SAID PERMANENT MAGNET DRIVING MEMBER. 